Influenza vaccination protects individuals against infection, reduces absenteeism at work and missed days of school. The 2004-2005 flu season saw a substantial reduction in influenza vaccination rates due to a shortage in the supply of the influenza vaccine. Due to failure of a Chiron production plant, compared to previous years, there was approximately a 31 million-dose shortage of the influenza vaccine and vaccination rates in the country dropped by nearly 25%. In this proposal we aim to take advantage of this natural experiment to estimate the effect of this reduction in vaccination supply on a variety of outcomes including health care utilization, mortality, work productivity and school absenteeism. Specifically, we take advantage of the fact that states that ordered vaccinations specifically from Chiron were more likely to experience a vaccine shortage than states that did not order their vaccinations from Chiron. Calculations of state level vaccination rates from the Behavioral Risk Factor Social Survey data indicate substantial cross-state variation in reductions in vaccination rates due to the shortage, with some states experiencing nearly a 40% reduction in vaccination rates while other states experienced little to no reduction. In the analyses, using unique data from the CDC on state vaccination orders specifically to Chiron, we first instrument for the reduction in state vaccination rates in the 2004-2005 flu season. We then estimate the impact of this reduction on state level measures of health care utilization, influenza mortality, work productivity and school attendance. Compared to previous work in this area, our study promises to provide comprehensive estimates of the effects of the vaccination on these outcomes since we are able to capture these outcomes for both vaccinated and unvaccinated individuals in these states. A more comprehensive accounting of the benefits of vaccination has the potential to affect policy maker decision making with respect to the utilization of the influenza vaccination to increase population health.